Inflatable packers are sealing devices that may be carried on a conveyance in a retracted position into a wellbore and then expanded to provide a seal against the wellbore wall or conduit. Inflatable packers typically include an inner elastomer bladder that is connected at its ends by moveable mechanical fittings to a mandrel. Commonly, a retaining cover comprising metal slats or cables is provided over the inner bladder to serve as the principal load bearing member when the packer is set and to prevent extrusion of the bladder when it is expanded. For example, slat-type packers typically comprise metal slats that are oriented longitudinally between the mechanical end fittings of the packers. The slats are positioned to substantially overlap when the bladder is retracted so that when the bladder is expanded the slats will provide a barrier against extrusion of the bladder. While the retaining cover provides anchoring against the wall and limits longitudinal movement of the assembly in the wellbore, it does not provide a fluid seal across the inflatable packer. Thus, it is common for inflatable packers to include a thick elastomer sleeve circumferentially about a portion of the retention member to provide sealing between the packer and the wellbore.
Drawbacks in the current outer sealing covers have been realized. One drawback is that in high temperature wellbores the outer sealing cover is often damaged or fails. For example, sealing may be lost and/or portions of the outer covering may part from the packer assembly. Another drawback of the outer rubber sealing covers is that in high pressure drawdown situations, the outer rubber cover tends to distend and move past or over the top of the mechanical end fitting. Positioning of a portion of the rubber covering over the mechanical end fittings can prevent removal of the packer from its set position.
FIGS. 1A and 1B illustrate a drawback of common inflatable packers. Referring to FIG. 1A, an inflatable packer assembly is expanded so that its outer rubber covering 3 is in sealing contact with the surrounding wellbore wall 5, illustrated herein as casing. The packer mandrel, inner bladder, and retaining cover are not illustrated in FIGS. 1A and 1B. Due to high temperature and/or high pressure differential across the packer assembly, rubber covering 3 is deformed and is displaced over one of the mechanical end fittings 7 as shown in FIG. 1B.
Therefore, it is a desire of the present invention to provide an inflatable packer that addresses drawbacks of current inflatable packers. It is a still further desire to provide an inflatable packer that includes a reinforced outer sealing cover.